Behind the scenes documentary following American professional tennis players Venus and Serena Williams. Coached by their father from a very young age, the Williams sisters trained up to six hours a day at local courts in Compton, California, before going on to win numerous junior competitions as well as many Grand Slam titles in their later professional careers. Although at times they have been the source of controversy and suspicion their abilities on the court have helped transform the world of women's tennis. The cameras follow the two sisters as they battle through one of the most difficult periods of their careers, with Venus suffering from an autoimmune condition and Serena recovering from a pulmonary embolism. The film also features contributions from John McEnroe, Billie Jean King and Anna Wintour.